1. Field of the Invention
The present invention relates to an above knee prosthesis and, more specifically, to a teaching playback swing-phase-controlled above knee prosthesis capable of storing patterns of walking speeds and of playing back the patterns of walking speeds.
2. Description of the Prior Art
There have been proposed various above knee prostheses designed so that the wearers of the above knee prostheses may not be easily identified by the above knee prostheses and the wearers of the above knee prostheses may not be subject to physical and mental stress.
An above knee prosthesis disclosed in Japanese Patent Publication (Kokoku) No. 52-47638 comprises a thigh frame, a leg frame pivotally joined to the thigh frame for turning relative to the thigh frame, and an air cylinder having a cylinder sealing air therein, and a piston fitted in the cylinder and provided with a valve, and interconnecting the thigh frame and the leg frame. The opening of the valve of the cylinder is adjusted properly to control the sliding speed of the piston by changing the resistance against the flow of air through the valve so that the leg frame is able to swing relative to the thigh frame according to a predetermined walking speed.
With this previously proposed above knee prosthesis, however, the resistance against the flow of air through the valve must be adjusted to a specified value and the wearer is able to walk only at a walking speed corresponding to the specified value, which has been quite inconvenient to the wearer.
Recently, swing-phase-controlled above knee prostheses have been proposed, for example, in Japanese Patent Laid-open (Kokai) Nos. 1-244746, 1-244747 and 1-244748, which correspond to U.S. Pat. Nos. 5,062,856, 5,133,773 and 5,133,774, British Pat. Nos. 2,216,426 and 2,252,503, and German Pat. Application No. P3909672. These previously proposed swing-phase-controlled above knee prostheses are capable of automatically selecting a walking speed among a plurality of walking speeds determined for the wearer, according to the wearer's intention.
Data is set during the walk training of the wearer wearing the previously proposed swing-phase-controlled above knee prosthesis.
A speed setting switch is set to a low-speed position and the opening of the valve of the cylinder is adjusted with an adjusting screw driven by a stepping motor to set the opening of the valve for a low walking speed. While the wearer is walking at the set walking speed, swing phases and stance phases are detected by means of a weight sensing means. When the above knee prosthesis is standing on the ground, i.e., while the above knee prosthesis is in the stance phase, the weight sensing means measures the wearer's weight. The time of duration of the operation of the weight sensing means in the stance phase is divided by the number of steps to determine the average stance phase duration time, and the average stance phase duration time and the corresponding opening of the valve are stored as data for a low-speed walking mode.
Similar data setting procedures are carried out for a middle-speed walking mode and a high-speed walking mode.
After the average stance phase duration time and the opening of the valve for each walking mode have been stored, the wearer starts walking at an optional walking speed. While the wearer is walking, the stance phase duration time is determined on the basis of the time in which the weight sensing means is in operation, the stance phase duration time and the previously stored average stance phase duration time are compared by using a predetermined expression, and then an opening of the valve among openings of the valve stored beforehand is selected on the basis of the result of comparison to enable the wearer to walk at a walking speed corresponding to the selected opening of the valve.
Incidentally, a practical above knee prosthesis, in general, has a soft covering imitating the leg.
Since the adjusting screw and the speed setting switch of the foregoing known above knee prosthesis are mounted on the structural body, the adjusting screw and the speed setting switch cannot be operated for adjustment and data setting when the structural body is covered with the soft covering. Since the swing motion of the leg frame is subject to the resistance of the soft covering, the data obtained through trial walking with the soft covering put on the structural body and the data obtained through trial walking with the soft covering removed from the structural body are necessarily different from each other.